The provision of service in the event of interruption of a transmission link has conventionally been accomplished by means of standby transmission links. Whereas one standby link may be provided for several working links, this practice does not provide a solution for a transmission configuration of potential interest using optical fibers. For example, it may be economically advantageous to handle two or more fibers as a single unit, forming them into a tape-like array and mating them with repeaters using a single plug-in connector. The detectors, LEDs, and lasers can be fabricated in arrays on single chips of semiconductors, and the electronics made on a single chip for several repeaters. When maintenance is required on any one of these elements, all of the transmission links passing through the single tape assembly are interrupted. Thus, there is a strong motivation to arrange the transmission so that usable (but somewhat degraded) transmission can be maintained when a link is broken (perhaps only for a few seconds).